1. Technical Field of the Invention
The present invention relates generally to signal generators, and specifically to download of waveforms to signal generators.
2. Description of Related Art
Signal generation test instruments are utilized in the wireless telecommunications industry to aid in the measurement of the quality of signals transmitted and received over wireless transceiver equipment. A signal generation test instrument includes an RF signal generator that is modulated by a waveform generator. The waveform generator uses a composite modulation technique to encode information in both the amplitude and phase of the modulated signal. Specifically, the waveform generator generates digital samples corresponding to the base-band I (in-phase) and Q (quadrature-phase) components. A set of numerical value pairs (I and Q) of the digital samples that are converted into analog form constitutes the waveform. Since the waveform and signal generation test instrument are specifically calibrated and produce a known signal, the signal generation test instrument can use the waveform to perform measurements on the wireless equipment.
Different types of composite modulation techniques are used for different types of communications formats, such as, Code Division Multiple Access (CDMA) and Time Division Multiple Access (TDMA). Therefore, instead of using a different signal generation test instrument for each modulation technique, computer-generated waveforms can be downloaded to a generic signal generation test instrument that is capable of transmitting any type of waveform. For example, the generic signal generation test instrument (hereinafter referred to as a signal generator) can be customized to transmit any type of waveform by taking downloaded I and Q values, converting the I and Q values into analog signals through the use of a digital-to-analog converter and using the analog signals to modulate a carrier (i.e., “play” the waveform).
A user can access signal generation software stored on a computer, and configure one or more waveforms for one or more communications formats. The signal generation software includes a different application for each type of communications format. In addition, each signal generator includes one or more “licensing keys”, each being associated with a different application. These licensing keys are purchased from the signal generator provider, and prevent unauthorized use of the software. Upon creation of a particular waveform, the signal generation software within the computer checks the signal generator connected to the computer for the appropriate key prior to downloading the waveform to the signal generator.
The waveforms themselves are not stored on the computer containing the signal generation software or in any other location other than the specific signal generator equipment that the waveform was created for, in order to prevent unauthorized equipment from utilizing the waveforms without purchasing a key. However, by requiring the waveforms be stored directly on the signal generator, many test customers who utilize automatic test equipment systems are not able to implement an automated signal generation solution.
Automatic test equipment (ATE) systems are software-driven, meaning that there is no user-interaction involved. Therefore, ATE systems do not allow a user to manually create a waveform on a computer and download that waveform directly to a signal generator connected to the computer. Instead, ATE systems include software for instructing a signal generator to generate a specific waveform. Therefore, what is needed is a mechanism for storing waveforms on the computer, while maintaining security of the waveforms, in order to provide an ATE solution.